This invention relates to a twist capsule which conducts signals between an input and an output which are rotatable relative to one another around an axis of the twist capsule.
Devices for conducting signals between two points which are rotatable relative to one another are well known in the art. Such devices or rotary joints comprise slip rings which are used when unlimited rotation is required, and twist capsules which are used when only limited rotation is required. The present invention relates to twist capsule in which only limited rotation of the capsule around its axis is required. Such a structure is shown in U.S. Pat. No. 3,599,165 issued to Wendell et al.
The Wendell et al patent shows a twist capsule in which a flat cable is wound in a spiral around the axis of the twist capsule. The inner and outer portions of the capsule are rotatable relative to one another in both clockwise and counterclockwise directions. Such rotation causes a coiling and uncoiling of the spirally wound flat cable around the capsule axis and around itself. Over a period of extended use, the coiling causes an abrasion of the cable insulation which can lead to capsule failure. Additionally, because one end of the flat cable is located in the center of the spiral, individual leads must be attached to the ends of the flat cable in order to connect the cable to external wiring. The attachment of the leads to the flat cable is time consuming and adds undesirable cost and complexity to the capsule assembly.
It would, accordingly, be desirable to construct a twist capsule without a spiral wrap to avoid the above mentioned drawbacks of internal abrasion and lead attachment.